Plug valve having a dual diaphragm three position actuator

ABSTRACT

A combined plug valve and dual diaphragm three position actuator assembly wherein the actuator comprises a two part housing having two diaphragms clamped therebetween, the diaphragms being separated by a spacer ring and a fluid communication passage therethrough to a chamber formed by the diaphram. Two more chambers are defined by the outer surfaces of the diaphragm and the housing, and each chamber has a fluid communication passage thereinto. Springs in two of the chambers bias the diaphragms apart; one spring is located between the two diaphragms and includes a collapsible link unit to limit separation of the diaphragms. An operator rod extends through the housing from one of the diaphragms and is secured to a rotary operative lever on the plug valve. Thus assembled, the actuator operates the valve through three positions.

United States Patent [191 Johnson [54] PLUG VALVE HAVING A DUALDIAPHRAGM THREE POSITION ACTUATOR [75] Inventor: Jesse R. Johnson,Gowanda, N.Y.

[73] Assignee: AVM Corporation,

[22] Filed: April 12, 1971 [21] Appl. No.: 132,958

Related US. Application Data [60] Division of Se r'l N0. 72336Z A pril24, 1968,

Pat. No. 3,613,513.

Jamestown,

[52] US. Cl. ..25I/58, 251/61, 92/48 [51] Int. Cl. ..F16k 31/165, FOlb19/00 [58] Field of Search ..251/58, 61; 92/48, 49

[56] References Cited UNITED STATES PATENTS 3,187,640 6/1965 Young etal. ..92/48 2,973,181 2/1961 Johnson ..25l/3l7 X 3,265,373 8/1966 Walkeret al. ..25 H6] X [4511 Jan. 9, 1973 Primary Examiner-Arnold RosenthalAttorney-Strauch, Nolan, Neale, Nies & Kurz [57] ABSTRACT A combinedplug valve and dual diaphragm three position actuator assembly whereinthe actuator comprises a two part housing having two diaphragms clampedtherebetween, the diaphragms being separated by a spacer ring and afluid communication 7 passage therethrough to a chamber formed by thediaphram. Two more chambers are defined by the outer surfaces of thediaphragm and the housing, and each chamber has a fluid communicationpassage thereinto. Springs in two of the chambers bias the diaphragmsapart; one spring is located between the two diaphragms and includes acollapsible link unit to limit separation of the diaphragms. An operatorrod extends through the housing from one of the diaphragms and issecured to a rotary operative lever on the plug valve. Thus assembled,the actuator operates the valve through three positions.

10 Claims, 28 Drawing Figures PAIENTEDJAN 91915 SHEET 1 BF 3 INVENTORJesse A? Jab/2500 ATTORNEY 5 PATENTEDJAH 91ers 3.709.461

SHEET 2 OF 3 r54 I-IZ- L ae FIG. I]

62 FIG 8 I INVENTOR 68 Jesse R Johnson WW' W W W ATTORNEYS Pmmmm 9191a3.709.461

' SHEH 3 BF 3 FIG I4 INVENTOR Jesse E. Johnson wild, ifr lw 7fuf3/w2/ATTORNEYS PLUG VALVE HAVING A DUAL DIAPHRAGM THREE POSITION ACTUATORCROSS REFERENCE TO RELATED APPLICATION This is a divisional applicationof Ser. No. 723,862, filed Apr. 24, 1968, now US. Pat. No. 3,613,513.

BACKGROUND OF THE INVENTION This invention relates to combinedmulti-position expansible chamber actuators and plug valve assemblies,and more particularly to a three position actuator operatively connectedto a three position plug valve, useful for controlling windshieldwipers, fresh air dampers, and similar fluid flow apparatus onautomotive equipment or other such structures.

Plug valves combined with differential or vacuum pressure expansiblechamber motors to operate the valves are well known to those skilled inthe art, and it has been previously proposed to utilize such assembliesparticularly in the automotive field. However, a substantial majority ofpreviously known multi-position vacuum actuated plug valve assemblieshave not received widespread acceptance because of their complexconstruction both as to plug valve support and operator lever structureand actuator piping, internal valving, requisite external valving, andphysical characteristics, primarily overall length of the actuator housing needed to accomodate components for three position actuation.

SUMMARY OF THE INVENTION It is a principal object of the invention toprovide a novel three-position vacuum actuated plug valve assemblyhaving a minimum number of parts, being economical to manufacture, andhaving a substantially reduced overall length.

Another object resides in the provision of a threeposition vacuumactuated plug valve assembly wherein the actuator comprises a housingenclosing two spaced diaphragms with a connection therebetween to asource of vacuum through an edge opening in the housing, one of thespaces defined by one diaphragm and the housing also having a throughconnection to a vacuum source.

Another object of the present invention resides in the provision of adual diaphragm three position vacuum actuated plug valve assembly inwhich the operator rod from the actuator and the plug valve controllever are interconnected in such a manner as to avoid chatter andinaccurate plug valve positioning at a third, intermediate actuatorposition. More specifically, the interconnected relationship permits asmuch as a ten degree deflection from a straight push-pull path withoutaffecting operational efficiency.

A still further object resides in the provision of a novel compact dualdiaphragm three position actuated plug valve assembly including positiveconnections between the actuator operator rod and the plug valve controllever enabling three position control of the plug valve. In particular,the actuator operator rod is deflectable to establish an intermediateflow position in the plug valve, between its fully closed and fully openconditions.

Still another object of the present invention resides in the provisionofa dual diaphragm multi-position actuated plug valve assembly whereinthe diaphragms of the actuator include a lost motion collapsing link assembly therebetween to positively limit separation of the diaphragms onefrom the other, an operator rod being secured to one of the diaphragmsand the control lever of the plug valve.

Other objects reside in the provision of a novel, highly compactthree-position dual diaphragm actuated plug valve assembly wherein theactuator requires no external projection to accomodate the threeposition feature, the diaphragms are interconnected by a lost motioncollapsing link assembly which can fold into minimum space normallyexisting between collapsed diaphragms, parts may be made of metal ornon-metallic material depending on environmental operation conditions,and a spacer ring and additional spacing means may be provided betweenthe diaphragms to prevent sealing engagement of one to the other whenthe space therebetween is evacuated.

Further novel features and other objects of this invention will becomeapparent from the following detailed description, discussion and theappended claims taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS Preferred structural embodiments of thisinvention are disclosed in the accompanying drawings in which:

FIG. 1 is a sectional view of a preferred embodiment of an actuator madein accordance with the present invention, illustrating the extendedposition of the actuator operating rod when neither of the operatingchambers have a vacuum source connected thereto;

FIG. 2 is a sectional view similar to FIG. 1 showing the operator rodand the two diaphragms in shifted position when the rear chamber issubjected to vacuum;

FIG. 3 is a sectional view similar to FIGS. 1 and 2 showing the positionof the operator rod and diaphragms when vacuum is applied to theoperating chambers (middle and rear) and the link assembly betweendiaphragms is in a fully collapsed condition;

FIG. 4 is a side elevation view showing a three position actuatorassembled in combination with a valve controlled thereby in accord withthe present invention;

FIG. 5 is a partial front elevation view of the assembly shown in FIG. 4and illustrates the connection between the actuator operator rod and thevalve plug rotating lever;

FIGS. 6 and 7 are enlarged side and front views, respectively, of thepreferred metal embodiment of the collapsible link assembly;

FIG. 8 is an enlarged detail section through a portion of the actuatorhousing and spacer ring to illustrate details of the cooperatingstructure;

FIG. 9 is a partially sectioned side view of one of the diaphragms;

FIGS. 10 and II are enlarged plan and side views, respectively, of oneembodiment of the diaphragm support discs which include collapsible linkanchoring parts;

FIGS. 12-28, which illustrate various embodiments of collapsible linkunits as well as several suitable modifications of other actuatorcomponents, are generally described as follows:

FIGS. 12 through 14 illustrate use of a steel spacer ring and a moldednon-metallic, X-shaped collapsible link unit;

FIGS. 15 and 16 are detail views which illustrate a double loopcollapsible link unit constructed with molded, diamond shapednon-metallic units;

FIGS. 17 and 18 are detail views which illustrate a single wide bandcollapsible link unit made from nonmetallic material;

FIGS. 19 and 20 are detail views which illustrate use of a non-metallicO-ring as the collapsible link unit between two diaphragms;

FIGS. 21 and 22 are enlarged O-ring sections illustrating fabricreinforced O-rings which can be used as the collapsible link unit shownin FIG. 20;

FIG. 23 depicts a thin flat plastic ring which can be used in lieu ofthe O-ring unit in FIG. 20;

FIGS. 24-27 are detail views illustrating metallic torsion springembodiments of a collapsible link assembly, FIGS. 26 and 27 beingenlarged plan views of the two different torsion springs which are used;and

FIG. 28 is a perspective view of an alternative embodiment of thecollapsible link diaphragm anchor disc which can be used in lieu of thediaphragm support disc shown in FIGS. 10 and 11.

With reference to FIGS. 4 and 5, a three position vacuum actuator ormotor 30 is illustrated in assembly with a rotary plug valve 32, anexample of which is depicted in U.S. Pat. No. 2,973,181. The combinedactuator'valve assembly shown in FIG. 4 can be used in automotiveheating systems and cooling systems, in which, for example, twodifferent rates of flow of fluid through the valve as well as a valveshut-off condition are desired. The actuator could be used to operatesomething other than the depicted valve for example, and again referringto the automotive field, it may be used for setting the positions ofheater duct dampers and outlet control doors. Suitable sources ofvacuum,

e.g., 10 to 20 inches Hg, are normally available in automotiveinstallations and the present actuator can utilize such available vacuumpressures.

In the assembly shown in FIG. 4, both the actuator 30 and the valve 32are mounted on a sheet metal support bracket 34, the actuator beingsecured by bent over lugs 36 which are part of the actuator housing, aswill be more fully described, and the valve body 38 being similarlysecured by bent lugs to a right angled platform portion 40 of the samebracket. In lieu of the lugs 36, threaded studs 37 (see FIG. 12) weldedto the actuator housing can provide the means for fastening the actuatorto a support structure. The actuator in FIGS. 4 and 5 is illustratedwith an L-shaped round operator rod 42, its terminal end 44 being bentto provide a portion which fits into an aperture in and serves tooperatively connect with the valve plug rotating lever 46. The valveplug stem 48 is secured to its operating lever 46 by staking. When theactuator operator rod 42 is in the extended condition, the valve is inits open condition with lever end 50 abutted against limit lug 52. Whenactuator 30 is moved to its other limit position, rod 42 is retractedcausing valve operating lever 46 to swing and rotate the valve plug to avalve full closed condition in which the other end 54 of lever 46 willabut a second limit lug 56. The intermediate position of the threeposition actuator locates the valve lever 46, with the plug,intermediate the two limit conditions.

Upon reviewing FIG. 5, it will be understood that the actuator operatorrod 42 must tilt, relative to its illustrated alignment with the inlineaxis of the actuator housing, as it is retracted and the valve lever 46swings in an are between its limit conditions. This feature of theactuator operator rod tilting or deviating from a straight line path isaccommodated by the internal construction of the actuator and is nownoted inasmuch as the exemplary actuator-valve assembly discloses onemanner in which this ability, not normally present in three positionactuators, can be utilized while avoiding the need for additionalarticulation links which are expensive and require added space.

Instead of making the actuator operator rod from round rod stock asshown in FIGS. 4, 5 and 12, it can be and is preferably made from flatbar stock in the manner of rod 104 shown in FIGS. 1, 2 and 3, thedetails of which will now be described.

Shown in FIGS. 1, 2 and 3, is a preferred construction of an actuator 60which is functionally the same as actuator 30. Actuator 60 is a threeposition, dual diaphragm, spring return vacuum actuator, in which thetwo diaphragms 62 and 64 are contained within a two part casing orhousing 66 consisting of a cup 68 and a cover 70. The housing parts canbe pressed from sheet metal or molded from suitable plastics, thematerial used normally being dictated by the environmental temperature.The outer peripheries 72 and 74 respectively of the two diaphragms 62and 64 are spaced apart by a spacer ring 76 and are clamped in sealedrelationship between portions of the housing 66 and adjacent endsurfaces of the spacer ring 76 when housing cover is secured to the cup68. Cup 68 has a lateral peripheral flange 78 which with the peripheriesof the diaphragms and the spacer ring fit into a stepped peripheralconstruction 80 on the cover 70. The peripheral extremity 82 of cover 70is bent inwardly, over the cup flange 78 and rigidly secures andsealingly clamps the two diaphragms and spacer in assembly within thehousing.

A vacuum connector 84 extends outwardly from the outer periphery of thespacer ring 76 and provides a fluid passageway 86 from the exterior tothe interior of the housing into the middle chamber 88 between the twodiaphragms. Shown in FIG. 5, the stepped periphery 80 of cover 70 isnotched at 89 to permit assembly of the component.

A second vacuum connector 90, fastened to the wall of cup 68, provides afluid passageway from the exterior to the interior of the chamber 92between the cup and diaphragm. (Chamber 92 for convenience will bedesignated the rear chamber). In the embodiment of FIGS. 1, 2 and 3, theend wall 94 of cup 68 is apertured with an inwardly directed slightextrusion 96 into which the end of connector is fitted and suitablybonded. When both the cup and the connector are made from metal, as ispreferable for higher temperature installations, the bonding can be madewith silver solder. When cup and connector are made from plastic (lowertemperature operating conditions) they can be molded as a unit or joinedby suitable plastic bonding agents. Whenever the connection 90 is madethrough the cup end wall 94, the inward wall extrusions 96 can betolerated and moreover provides a smooth finished appearance.Alternatively the vacuum connection 90 (FIG. 4) can be located throughthe side wall portion of the cup, in which case the pierced wall openingwill have its edges 96 extruded outwardly to avoid interference with anddamage to the rear chamber diaphragm, when it is pulled against the wallof the cup under application of vacuum.

In any case two connections for vacuum are provided, one to the middlechamber 88 and the other to the rear chamber 92. The chamber 98 (whichwill be designated as the front chamber for convenience) providedbetween the diaphragm 64 and cover 70 is open to ambient or atmosphericpressure through a cover opening, e.g., the central opening 100 in thecover end wall 102. The actuator operator rod 104, which is directlyconnected to front diaphragm 64, projects through the cover opening 100.

The inner peripheries of the two diaphragms 62 and 64 are firmly clampedbetween two metal support plates or discs made with slightly cuppedouter peripheries. Disc plates 106 and 108 are coaxially clamped on thefront diaphragm by a centrally located rivet 110 and disc plates 112 and114 are clamped on the rear diaphragm by a centrally located rivet 116.The outer discs 106 and 114 are similar to each other and the respectiveinner or facing discs 108 and 112 are similar to each other. Rivet 116merely serves only to clamp the rear discs 112 and 114 on the reardiaphragm whereas the slightly longer front rivet 110 also serves tosecure the flat operator rod 104 to the front diaphragm, passing throughan aperture in bent end 118 of rod 104, before it is riveted to tightlyclamp the rod 104, discs 106 and 198 and diaphragm 64 as a unit. Eventhough the flat rod 104 is tightly secured by rivet 110 it can beswiveled by exerting a twist in order to vary its disposition toaccommodate different installations. When a round rod operator link isused, as in FIGS. 4,5 and 12, its end is reduced and serves as thefastening member in lieu of rivet 110.

Inasmuch as the inner discs 108 and 112 are similar, a description ofone disc 108, FIGS. and 11, will suffice for both. Disc 108 has twointegral bent up, apertured ears 120 and 122, the ear apertures beingdisposed on a diametral center line of the disc as seen in the FIG. 10plan view and spaced on either side of the central rivet hole 124. Ears120 and 122 on the two inner discs serve as anchor devices for acollapsible link unit which will be hereinafter described. The cuppedouter periphery 126 of disc 108 is representative of all four of thediaphragm discs and in the case of three of the discs serve as a coilspring seat.

Returning to FIG. 1, the actuator contains two coil compression springs128 and 103, spring 128 being placed between the two diaphragms, seatedwithin the peripheries of the inner discs I08 and 112 and spring 130being placed in the rear chamber with one end seated within the cuppedperiphery of disc 114. The end wall 94 of the housing cup 68 has afrustum shape to provide a spring seat for the other end of rear spring130.

Spring 128 biases the two diaphragms 62 and 64 apart with sufficientforce to enable operation, through the operator rod 104, of the unitbeing operated, e.g., provides a force sufficient to rotate the valveplug shown in FIGS. 4 and 5. Similarly, spring 130 biases the reardiaphragm 62 away from the rear wall 94 of cup 68 with substantially thesame force as provided by spring 128. The spring forces for both springsare chosen so the springs will be readily compressed upon application ofvacuum to the respective chambers in which they are disposed.

A collapsible link assembly or unit 132, located in the middle chamber88, is fastened to each diaphragm by means of the support disc anchorears and 122 shown in FIGS. 10 and 11. In the preferred embodimerit,collapsible link unit 132 {see FIGS. 6 and 7) is made from three piecesof steel, two of which are similar bail shaped wire links 134 and 136and the third piece is a wide sheet metal link 140. The ends of the legsof both wire links 134 and 136 are bent outwardly to provide short pivotstubs 138. The tv 'vo wire links 134 and 136 are pivotally secured toeach other at their bight or mid-portion by a small sheet metal, formedlink 140. Link 140 has central opposed edge flange portions 142 and 144wrapped around the bights of the two wire bails to retain them inassembly and at the same time permit free relative pivoting betweenlimits. At each end of the sheet metal retaining link 140, two integraltabs 146 and 148 extend beyond both sides of the bights of the two wirelinks, and serve as limit abutments for the legs of the two wire links134 and 136. The tabs 146 and 148 have an intentional curvature whichlimits the outward pivoting of links 134 and 136 to approximately thedisposition shown in FIGS. 1, 2 and 6. The limit stop arrangementprevents a full pivoting of the link unit 132 and avoids a dead centeror over center disposition of the two wire links which could result in acondition where the link assembly would not collapse when the middlechamber is evacuated.

The bent stub ends 138 of the: wire links pivotally fit into theapertured anchor ears 120 and 122 in the inner diaphragm discs 108 and112 as shown in FIGS. 1, 2 and 3. Because of the resilience of the steelwire links, the pivot ends on the legs of each link can be squeezedslightly together and sprung into anchored disposition with associatedears 120 and 122 on the facing diaphragms support discs. Thisrelationship can be visualized by viewing FIGS. 7 and 11 together.

Referring again to FIG. 1, the three piece collapsible link unit 132fastened between diaphragms 62 and 64, being made from metal, provides adefinite limit to the distance which the centers of diaphragms can bespaced apart due to force of the spring 128. The link unit serves as anarticulated connection as well as to delimit a fixed distance betweenthe diaphragm attached end of operator rod 104 and the rear diaphragm67. Collapse of the link unit must be assured to permit the diaphragmsto move toward each other, when vacuum is applied to the central chamber88, at least to the limit permitted by compression of the coil spring128.

The three positions of the actuator, from which it derives its typedesignation, are illustrated respectively in FIGS. 1, 2 and 3. Controlof application of the vacuum or low pressure source will be via one ormore manual or automatic control valves (not shown) as desired for theinstallation.

FIG. 1 represents the first position, the spring biased extendedposition of the actuator, in which there is no vacuum applied to eitherof connectors 84 or 90, the lines (not shown) which fasten to suchconnectors being opened to ambient pressure surrounding the actuatoritself. Pressures being equalized on both sides of both diaphragms, thebias of spring 128 against the support discs of both diaphragms willforce them apart to the limit distance permitted by collapsible linkunit 132 and at the same time rear spring 130 will force the reardiaphragms via its support discs toward the cover end of the housing.This combined spring force results in the front diaphragm disc 106moving to abut against the cover end wall 102, at which limit, theattached operator rod 104 is moved out to its fully extended position.The force exerted by the springs to urge the operator rod 104 to itsextended position will be selected as desired for a particularinstallation. One installation in which the actuator will actually beused requires at least a 3.5 pound force to be exerted in urging theactuator rod to extended position, hence the spring compression force ofeach spring would be at least 3.5 pounds. While it is preferred that theactuator be a complete bi-directional motor with self contained springsfor urging the actuator operating rod in the one direction, the springscould be omitted from inside of the actuator housing, in which event thecomponent being operated could be spring loaded to pull the operator rod104 to the extended limit position shown in FIG. 1, and vacuum operationof the actuator would work in opposition to the external spring.

FIG. 2 illustrates the No. 2 or intermediate actuator position wherein asource of vacuum has been connected to the rear chamber 92 via connector90 permitting differential pressure across the rear diaphragm 62 toforce diaphragm 62 toward the rear wall 94 of the cup to its position aslimited by compression of the coil spring 130. This movement ofdiaphragm 62 is transmitted through its support discs 112 and 114 andthe collapsible link unit 132 (which will now be fully extended) to pullthe front diaphragm 64, through its support discs, toward the rear wall94 and thereby retract the operator rod 104 to its intermediateposition. The vacuum source must provide a pressure differential,relative to ambient pressure, which when applied to the effectivepressure area of the diaphragm 62 will exert enough force to overcomethe bias of spring 130 and still provide the requisite specified pullingforce on the actuator rod 104. FIG. 2 also clearly illustrates that thewall of diaphragm 62 conforms closely against the inside surface of thecup 68 as it moves toward the rear wall 94. While this is normal in suchdiaphragm motors, and causes no problem, the situation is different andthere can be a problem in connection with movement of the frontdiaphragm 64 as will be described in the next portion pertaining to theNo.3 position.

To shift to the No. 3 position shown in FIG. 3, the

vacuum source is applied to both the rear chamber 92 and the middlechamber 88, via respective connectors 90 and 84. Applying or continuingthe connection of vacuum to connector 90 evaeuates the rear chamber 92placing the rear diaphragm 62 in the condition previously described forposition No. 2. Evacuation of the middle chamber 88 through theconnection 84 and passageway 86 in spacer ring 76 causes a pressuredifferential across the front diaphragm 64 to move it from the covertoward the rear diaphragm 62, compressing the coil spring 128 to itscompact limit condition as shown in FIG. 3. As the diaphragm 64 movescloser to diaphragm 62, its support discs 106 and 108 force the linkunit 132 to collapse to its folded condition and at the same timeretract the operator rod 104 into the housing 66 to its maximum retractposition No. 3. It should be apparent that the precise location of theNo. 3 position can be changed by using a different number of coils ineither or both of springs 128 and 130 and that the precise location ofthe No. 2 position can be changed by using a different number of coilsin spring 130 or by changing the length of the legs on the wire formlinks in the link unit 132.

The previously mentioned problem which can be encountered in connectionwith front diaphragm 64 is occasioned by the fact that as the diaphragmmoves toward the rear with middle chamber 88 connected to a vacuumsource, the diaphragm wall rolls across and attempts to conform to thesurface of the inner periphery of the spacer ring 76 and as its movementprogresses it progressively moves into tight conformity with the frontsurface of the rear diaphragm 62 which will be flat against the innerside surface of the cup 68. The conformity of the flexible diaphragmwall against the spacer surface could immediately shut off thepassageway 86 and prevent further evacuation of the middle chamber 88.To alleviate blocking of the outlet passage 86, at least the frontdiaphragm 62 is provided on its rear surface with a series of spacedapart small radial ribs 152 (seen in FIGS. 1, 2 and 9) which will createmultiple radial passageways between overlapped surfaces to allow air tobe exhausted from chamber 88 between the two engaged diaphragms.

To further assure that evacuation blocking does not occur, the spacerring inner periphery is relieved. A preferred manner of relief is toundercut a portion 154 (see FIG. 8) of the inner periphery of spacerring 76. Such an undercut portion is shown disposed closest to the reardiaphragm 62, although it can be disposed either way, and will intersectthe lateral passageway 86. When the front diaphragm 64 in its initialmovement rolls over the step 156 formed by the undercut 154, it will notconform into a small annular passageway along the corner of the undercut154. Since the annular corner passage connects with the passageway 86,blocking or sealing off of the passageway 86 by the diaphragm 62 isprevented. An alternative expedient is shown in FIG. 12 where an annulargroove 158 is provided around the inner periphery of the spacer ring.The undercut or stepped embodiment is preferred as it more readily lendsitself to inexpensive molding of the spacer ring from plastics than doesthe groove embodiment. Also, when steel rings are used, the undercut canbe machined more readily than the internal groove.

Shown in the sectioned detail view of FIG. 8, both the upper and lowersurfaces of spacer ring 76, at the outer peripheral edge of the ring,are provided with annular recesses I62 and 164 which, in clampedassembly, cooperate with an annular bead 166 on the outer periphery ofthe respective diaphragms. This relationship assures that the diaphragmsare not only sealingly clamped but are also effectively gripped at itsouter periphery to prevent their peripheries from being pulled out fromclamped assembly. As an additional gripping aspect, an annular rib canbe formed in the cooperating surfaces of the cup 68 and cover 70, e.g.,the rib 168 in flange 78 of cup 68 is shown in FIG. 8,

and such a rib 168 will provide a pressure fit around the periphery ofthe diaphragm and against the spacer ring radially inward of thediaphragm head 166.

The spacer ring 76 provides a stable rigid clamping structure which canbe satisfactorily accomplished with rings made from metal or plastic.Steel spacer rings are desirable where temperature conditionsapproximate 265F. or above whereas plastics have been successful andfound to be fully acceptable for environmental temperatures up to 220F.One plastic material found to be very satisfactory by itself and more sowhen fiber glass filled is CELCON, an ethyl cellulose thermoplastic.

The diaphragms can be made from rubber or similar materials as requiredto withstand conditions for various installations. A highly satisfactoryoil and temperature resistant material for the diaphragms in actuatorsused in the automotive field has been found to be a synthetic made fromethylene propylene by Vernay Laboratories, Inc., Yellow Springs, Ohio.It is known to the trade as EPT rubber.

Different structural embodiments of collapsible link units coupledbetween the two diaphragms in the three position actuator of the presentinvention are shown in FIGS. 12-27. Some of the collapsible link unitsare made from non-metallic materials and represent initial stages in thedevelopments which culminated in the preferred embodiment of the threepiece steel link unit, hereinbefore described.

FIG. 12, along with FIGS. 13 and 14 illustrate an embodiment of thethree position actuator which utilizes a rubber X-shaped collapsiblelink unit 172. The unit 172 is molded from a rubber material withminimum stretch characteristics. The molded end tabs 174 on the legs ofunit 172 are clamped under bent over integral punched tabs 176 in theopposed diaphragm support discs.

FIGS. and 16 illustrate a pair of what, for convenience, will be termeddiamond links 180 and 182 which, like the X-link 172, are molded fromrubber. In this embodiment of collapsible link assembly, auxiliarydouble hook plates 184 and 186 are secured respectively against each ofthe opposing diaphragm support discs by the support disc rivetconnection and the ends of the diamond links 180 and 182 are looped andfirmly fastened under the hooked ends of plates 184 and 186, as shown inFIG. 15.

FIGS. 17 and 18 illustrate the use of a wide rubber band 190 as thecollapsible link. The band 190 is pierced by apertures 192 and 194 atdiametrically opposite locations. The .rivet members of the twodiaphragms are used to secure the band 190 between the diaphragms, therivets passing through the respective rubber bands apertures 192 and 194and respective small clamping plates I96 and 198 before being riveted tosecurely clamp the plate 196 and 198, the band 190, the diaphragm andits discs together. The edges of the clamping plates 196 and 198 arebent up as at 199 and have a smooth finish to prevent damage to therubber band 190. Instead of being bent at 199, the edges of the smallclamp plates may be chamfered.

While all of the X-shaped link unit 172, the diamond shaped link units180 and 182 and the rubber band link unit 190 exhibit some stretchcharacteristics and are not intended to be used under extremes of loadand temperature conditions they are satisfactory to provide acollapsible connection having a determined maximum spacing withincertain tolerances between the two diaphragms to accomplish the threeposition operating function of the actuator under some condi- 5 tions.

FIGS. 19-23 represent several non-metallic collapsible embodiments whichexhibit ability to withstand more extreme conditions of temperature andforce than do the other rubber link units 172, 180 and 190, althoughagain these embodiments, using presently known materials, will not beused under extremes of temperature conditions to which many automotivecomponents are subjected.

FIG. 19 illustrates a collapsible link unit in which a single rubberO-ring 210 is booked in a bungee arrangement over double hook plates 212and 214 secured by riveting against the opposed diaphragm support discsin a manner similar to the hook plates in FIG. 15, although the hookplates will be arranged transverse to each to readily accommodate thelooped arrangement of the O-ring. To enable this embodiment ofcollapsible link unit to be used in actuators operating under somewhatgreater load forces without stretching and exceeding the desired maximumspacing limit between diaphragms, the rubber O-ring may be reinforcedwith a fabric material, along the inner or outer periphery of O-ring210' as shown at 216 in FIG. 21 or as a central core 218 of O-ring 210"as shown in FIG. 22.

A further embodiment which exhibits characteristics similar to theO-rings is a flat polypropolene ring 220 shown in FIG. 23. This ring isinstalled as a collapsible link unit in the same manner as hereinbeforein connection for O-ring 210.

A further embodiment of the collapsible link which exhibits satisfactoryand acceptable characteristics under all specified extremes ofautomotive operating 40 conditions is the metal torsion link embodimentillustrated in FIGS. 24-27. While substantially more expensive than thethree piece steel link unit 132, the torsion link unit 230 is consideredto have substantially the same reliability and will provide apre-determined maximum spacing distance between diaphragm support discswithin the very close tolerances provided by the three piece steel linkunit 132. i i

The torsion spring link unit 230 consists of two dissimilar small coiledtorsion springs 232 and 234 with associated steel wire anchors 236 and238. Springs 232 and 234, as seen in FIGS. 26 and 27, are coiled inopposite directions and in the relaxed spring condition have their twoterminal legs 240, 242 and 244, 246 extending in opposite directionsfrom the ends of the respective coils and disposed essentially in thesame plane. The ends 241 and 243 of respective legs of coil spring 232are made into loops which bend inwardly toward each other (FIG. 26)whereas the loop ends 245 and 247 of respective legs 244 and 246 of coilspring 234 coil in the same direction as does their coiled spring whichmakes them essentially perpendicular to the plane of their legs (FIG.27). Such dissimilarity will better accomodate coupling of the: twosprings. FIG. 25 illustrates the manner in which the: two spring units232 and 234 are fastened together, loops 241 and 245 being linkedtogether and loops 243 and 247 being linked together and all leg loopsbeing bent sufficiently to prevent separation. FIG. 25 also illustratesthe appearance of the torsion spring link unit in its collapsedcondition.

With the two springs of the torsion spring link unit 230 assembled asshown in FIG. 25, it will be connected, within the diaphragm biasingspring I28, to the opposed diaphragm support discs 250 and 252. Eachdiaphragm 62 and 64 with its two support discs having been previouslyriveted in assembly. The outer discs and the operator rod and itsconnection are all similar to the assembly described in conjunction withFIG. 1. The inner anchor discs 250 and 252 (the ones which oppose eachother in the assembled double diaphragm) are similar. One such disc 250is shown in FIG. 28 and has its anchor portions made by piercing anddeforming two diametrally located strips of the disc metal upward toform upstanding anchor loops 254 and 256 spaced a sufficient distanceapart to accommodate the coiled portion of one of springs 232 and 234between them. In FIG. 24, one spring 232 is anchored between strip loops254 and 256 of the disc 250 by slipping the short length of steel wireanchor 236 under one loop, through the spring coil and then under theother loop. The extremities of the wire anchor 236 are then bent overclose to the loops to prevent its dislodgement and to prevent engagementwith and damage to the diaphragms. The other spring 234 is anchored todisc 252 by its anchor wire 238 in a manner similar to that justdescribed.

This embodiment of anchor disc 250 constitutes one way of providinganchor components in the opposing diaphragm support plates and can beused as an alternative to the punched out and bent up apertured ears 120and 122 of the hereinbefore described anchor disc 108 shown in FIGS. 10and 11. An important advantage of the construction of anchor disc 250 isthat, using mass production techniques, the slightly less expense perunit will result in substantial savings.

Because of the manner in which the two springs of the torsion springcollapsible link unit 230 are interconnected, their normal torsion biaswill be toward the collapsed condition seen in FIG. 25. The torsion biasforce of the two springs 232 and 234 is substantially less than theforce of compression coil spring 128' located between the two diaphragmswhich shifts the coil por tions of torsion springs to the dispositionshown in FIG. 23 where each of the interconnected pairs of legs have anangular disposition approximately like that of the open wire form link132 seen in FIG. 2. In the opened link condition, the torsion springlegs, being biased back toward their collapsed planar condition, cannever reach a dead center condition and moreover will always moveimmediately toward collapsed condition under the torsion bias when avacuum source is applied to the middle chamber, between the diaphragms.

Although the hereinbefore described internal springs 128 and 130 arestraight coil springs, they could be cone shaped springs. The advantageof the straight spring is that the rate of change of power of the springis considerably less with a straight spring than with a cone spring.Thus the advantage accruing to the actuator by use of straight coilsprings is a nearer uniform power with a given amount of vacuum at bothends of the travel.

The disadvantage of the straight spring as against the cone shape springis that in closed position a cone shape spring is the thickness of thewire diameter while the straight spring in its closed position isconsiderably longer as is shown in FIG. 3. This feature of a cone springwill permit a shorter cup or housing. The straight spring providesbetter performance whereas a cone shape permits use of a smallerhousing.

The basic three position actuator can be used without using either ofthe internal springs 128 and 130 or an external spring (as was describedhereinbefore). Vacuum can be used in lieu of such internal springs andwill avoid loss of the built-in spring force which must be overcome bythe operating vacuum. In such an embodiment, the round rod arm such asrod 42 is'used with a shiftable seal arrangement provided between thefront chamber wall and the round rod arm, and a vacuum connector isattached to the wall of the front chamber similar to connector 90 asdescribed for the rear chamber. Operating vacuum is then selectivelyapplied to the front chamber as well as to the rear and middle chambersto cause actuator shift from and to all three positions.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by Letters Patent is:

l. The combination of a rotary plug valve, a multiposition expansiblechamber vacuum actuator and a common support mounting both said valveand actuator in assembled operative relationship; said valve including ahousing rigidly secured to said support and a control lever to rotatesaid plug; said actuator comprising housing means secured to saidsupport, at least two diaphragms secured within said housing to definetwo vacuum operating chambers, one of said chambers located in the spacebetween the two diaphragms, said diaphragms cooperating with saidhousing to provide fluid tight isolation between said operatingchambers, means providing fluid communication through said housing intoeach of said operating chambers from the exterior of said housing,motion transmitting means secured at one end to one of said diaphragmsexterior of said two operating chambers and projecting exterior of saidhousing,means coacting with said diaphragms urging them in a directioncausing maximum extension of said motion transmitting means from saidhousing including a collapsible device located between and connected toboth of said diaphragms enabling said diaphragms to move relativelytoward and away from each other between a substantially fixed maximumdistance at least when one of said chambers is selectively subjected tovacuum and a closely spaced adjacent disposition of said two diaphragmsat the end of said housing means opposite the motion transmitting meanswhen both of said chambers are subjected to vacuum; a pivot connectionbetween the other end of said motion transmitting means and said plugcontrol lever; and said collapsible device permitting tilting of atleast said one of said diaphragms and said motion transmitting meansrelative to said actuator housing means to accommodate an arcuateswinging of said pivot connection about the axis of the rotary plug ofsaid rotary plug valve as the actuator moves said rotary plug through anintermediate flow control position between its operating limitpositions.

2. The plug valve and actuator combination as deffined in claim 1,wherein said collapsible device located between and connected to saidtwo diaphragms comprises diaphragm support plate means secured to eachof said diaphragms in facing relationship, anchor means on each of saidsupport plate means, a collapsing link secured to both of said anchormeans, and means for positively preventing a non-collapsing condition ofsaid collapsing link when disposed in its extended position.

3. The plug valve and actuator combination as defined in claim 2,wherein said collapsing link comprises two U-shaped bails, the stemsthereof pivotally connected to said anchor means, said means forpositively preventing a non-collapsing condition of said link comprisinga bracket hinging the center portions of said U-shaped bails, and havingportions cooperating with said bails limiting extension thereof to lessthan a 180 disposition.

4. The plug valve and actuator combination as defined in claim 1,wherein said motion transmitting means comprises an elongate rod rigidlysecured at said one end to said one of said diaphragms.

5. The plug valve and actuator combination as defined in claim 4,wherein said pivot connection between the other end of said motiontransmitting means and said plug control lever comprises a cooperatingpin and aperture connection between the outer free end of said elongaterod and said plug control lever.

6. The plug valve and actuator combination as recited in claim 5,wherein said cooperating pin and aperture connection between the outerfree end of said elongate rod and said plug control lever comprises anL-shaped extension formed on said elongate rod free end and meansdefining a mating aperture for said L- shaped extension in the outerfree end of said plug control lever.

7. The combination of a rotary plug valve, an expansible chamber motoractuator and a common support mounting both said valve and actuator inassembled operative relationship; said valve including a housing rigidlysecured to said support and a control lever to rotate said plug; saidactuator comprising housing means secured to said support, at least twodiaphragms mounted within said housing to define two operating chambers,one of said chambers located in the space between the two diaphragms,said diaphragms cooperating with said housing to provide fluid tightisolation between said operating chambers, means providing fluidcommunication through said housing into each of said operating chambersfrom the exterior of said housing, motion transmitting means secured atone end to one of said diaphragms exterior of said operating chambersand projecting exterior of said housing, means coacting with saiddiaphragms urging them in a direction causing maximum extension of saidmotion transmitting means from said housing including a collapsibledevice located between and connected to said two diaphragms enablingsaid diaphragms to move relatively away from and toward each otherbetween a substantially fixed maximum distance and a closely spacedadjacent disposition of said two diaphragms and resilient expansion coilspring means disposed in said operating chambers, said coil spring meanstogether urging said diaphragms toward a maximum volume condition ofsaid operating chambers; and a pivot connection between the other end ofsaid motion transmitting means and said plug control lever; saidcollapsible device permitting tilting of at least said one of saiddiaphragms and said motion transmitting means relative to said actuatorhousing means to accommodate an arcuate swinging of said pivotconnection about the axis of the rotary plug of said rotary plug valveas the actuator moves said rotary plug through an intermediate flowcontrol position between its operating limit positions.

8. The plug valve and actuator combination as defined in claim 7,wherein said means providing fluid communication through said housinginto each of said operating chambers from the exterior of said housingcomprise independent piping means connected to independent vacuumsources for selective and combined evacuation of said operating chambersagainst the urging of said resilient expansion coil spring means.

9. The combination of a rotary plug valve, an expansible chamber motoractuator and a common support mounting both said valve and actuator inassembled operative relationship; said valve including a housing rigidlysecured to said support and a control lever to rotate said plug; saidactuator comprising housing means secured to said support, at least twodiaphragms mounted within said housing to define two operating chambers,one of said chambers located in the space between the two diaphragms,said diaphragms cooperating with said housing to provide fluid tightisolation between said operating chambers, means providing fluidcommunication through said housing into each of said operating chambersfrom the exterior of said housing, motion transmitting means secured atone end to one of said diaphragms exterior of said operating chambersand projecting exterior of said housing, means coacting with saiddiaphragms urging them in a direction causing maximum extension of saidmotion transmitting means from said housing including a collapsibledevice located between and connected to said two diaphragms enablingsaidl diaphragms to move relatively away from and toward each otherbetween a substantially fixed maximum distance and a closely spacedadjacent disposition of said two diaphragms; said housing means furthercomprise a spacer ring between said diaphragms urging the peripheries ofsaid diaphragms into fluid seal relationship with said housing, one ofsaid means providing fluid communication into said operating chamberscomprising a portion of said spacer ring and including a fluidpassageway through said spacer ring to said space between the twodiaphragms: additional spacing means located between said diaphragms forpreventing a fluid tight seal of one diaphragm against the other whensaid diaphragms are in said closely spaced adjacent disposition; a pivotconnection between the other end of said motion transmitting means andsaid plug control lever; and said collapsible device permitting tiltingof at least said one of said diaphragms and said motion transmittingmeans relative to said actuator housing means to accommodate an arcuateswinging of said pivot connection about the axis of the rotary plug ofsaid rotary plug valve as the actuator moves said rotary plug through anintermediate flow control position between its operating limitpositions.

10. The combination of a rotary plug valve, an expansible chamber motoractuator and a common support mounting both said valve and actuator inassembled operative relationship; said valve including a housing rigidlysecured to said support and a control lever to rotate said plug; saidactuator comprising housing means secured to said support, at least twodiaphragms mounted within said housing to define two operating chambers,one of said chambers located in the space between the two diaphragms,said diaphragms cooperating with said housing to provide fluid tightisolation between said operating chambers, means providing fluidcommunication through said housing into each of said operating chambersfrom the exterior of said housing, motion transmitting means secured atone end to one of said diaphragms exterior of said operating chambersand projecting exterior of said housing, means coacting with saiddiaphragms urging them in a direction causing maximum extension of saidmotion transmitting means from said housing including a collapsibledevice located between and connected to said two diaphragms enablingsaid diaphragms to move relatively away from and toward each otherbetween a substantially fixed maximum distance and a closely spacedadjacent disposition of said two diaphragms; a pivot connection betweenthe other end of said motion transmitting means and said plug controllever; said collapsible device comprising diaphragm support plate meanssecured to each of said diaphragms in facing relationship, anchor meanson each of said support plate means, a collapsing link secured to bothof said anchor means, and means for positively preventing anon-collapsing condition of said collapsing link when disposed in itsextended position; and said collapsing link comprising two U-shapedbails, the stems thereof pivotally connected to said anchor means, saidmeans for positively preventing a non-collapsing condition of said linkcomprising a bracket hinging the center portions of said U-shaped bails,and having portions cooperating with said bails limiting extensionthereof to less than a disposition: said collapsible device permittingtilting of at least said one of said diaphragms and said motiontransmitting means relative to said actuator housing means toaccommodate an arcuate swinging of said pivot connection about the axisof the rotary plug of said rotary plug valve as the actuator moves saidrotary plug through an intermediate flow control position between itsoperating limit positions.

1. The combination of a rotary plug valve, a multi-position expansiblechamber vacuum actuator and a common support mounting both said valveand actuator in assembled operative relationship; said valve including ahousing rigidly secured to said support and a control lever to rotatEsaid plug; said actuator comprising housing means secured to saidsupport, at least two diaphragms secured within said housing to definetwo vacuum operating chambers, one of said chambers located in the spacebetween the two diaphragms, said diaphragms cooperating with saidhousing to provide fluid tight isolation between said operatingchambers, means providing fluid communication through said housing intoeach of said operating chambers from the exterior of said housing,motion transmitting means secured at one end to one of said diaphragmsexterior of said two operating chambers and projecting exterior of saidhousing,means coacting with said diaphragms urging them in a directioncausing maximum extension of said motion transmitting means from saidhousing including a collapsible device located between and connected toboth of said diaphragms enabling said diaphragms to move relativelytoward and away from each other between a substantially fixed maximumdistance at least when one of said chambers is selectively subjected tovacuum and a closely spaced adjacent disposition of said two diaphragmsat the end of said housing means opposite the motion transmitting meanswhen both of said chambers are subjected to vacuum; a pivot connectionbetween the other end of said motion transmitting means and said plugcontrol lever; and said collapsible device permitting tilting of atleast said one of said diaphragms and said motion transmitting meansrelative to said actuator housing means to accommodate an arcuateswinging of said pivot connection about the axis of the rotary plug ofsaid rotary plug valve as the actuator moves said rotary plug through anintermediate flow control position between its operating limitpositions.
 2. The plug valve and actuator combination as deffined inclaim 1, wherein said collapsible device located between and connectedto said two diaphragms comprises diaphragm support plate means securedto each of said diaphragms in facing relationship, anchor means on eachof said support plate means, a collapsing link secured to both of saidanchor means, and means for positively preventing a non-collapsingcondition of said collapsing link when disposed in its extendedposition.
 3. The plug valve and actuator combination as defined in claim2, wherein said collapsing link comprises two U-shaped bails, the stemsthereof pivotally connected to said anchor means, said means forpositively preventing a non-collapsing condition of said link comprisinga bracket hinging the center portions of said U-shaped bails, and havingportions cooperating with said bails limiting extension thereof to lessthan a 180* disposition.
 4. The plug valve and actuator combination asdefined in claim 1, wherein said motion transmitting means comprises anelongate rod rigidly secured at said one end to said one of saiddiaphragms.
 5. The plug valve and actuator combination as defined inclaim 4, wherein said pivot connection between the other end of saidmotion transmitting means and said plug control lever comprises acooperating pin and aperture connection between the outer free end ofsaid elongate rod and said plug control lever.
 6. The plug valve andactuator combination as recited in claim 5, wherein said cooperating pinand aperture connection between the outer free end of said elongate rodand said plug control lever comprises an L-shaped extension formed onsaid elongate rod free end and means defining a mating aperture for saidL-shaped extension in the outer free end of said plug control lever. 7.The combination of a rotary plug valve, an expansible chamber motoractuator and a common support mounting both said valve and actuator inassembled operative relationship; said valve including a housing rigidlysecured to said support and a control lever to rotate said plug; saidactuator comprising housing means secured to said support, at least twodiaphragms mounted within said housing to define two operating chambers,one of said Chambers located in the space between the two diaphragms,said diaphragms cooperating with said housing to provide fluid tightisolation between said operating chambers, means providing fluidcommunication through said housing into each of said operating chambersfrom the exterior of said housing, motion transmitting means secured atone end to one of said diaphragms exterior of said operating chambersand projecting exterior of said housing, means coacting with saiddiaphragms urging them in a direction causing maximum extension of saidmotion transmitting means from said housing including a collapsibledevice located between and connected to said two diaphragms enablingsaid diaphragms to move relatively away from and toward each otherbetween a substantially fixed maximum distance and a closely spacedadjacent disposition of said two diaphragms and resilient expansion coilspring means disposed in said operating chambers, said coil spring meanstogether urging said diaphragms toward a maximum volume condition ofsaid operating chambers; and a pivot connection between the other end ofsaid motion transmitting means and said plug control lever; saidcollapsible device permitting tilting of at least said one of saiddiaphragms and said motion transmitting means relative to said actuatorhousing means to accommodate an arcuate swinging of said pivotconnection about the axis of the rotary plug of said rotary plug valveas the actuator moves said rotary plug through an intermediate flowcontrol position between its operating limit positions.
 8. The plugvalve and actuator combination as defined in claim 7, wherein said meansproviding fluid communication through said housing into each of saidoperating chambers from the exterior of said housing compriseindependent piping means connected to independent vacuum sources forselective and combined evacuation of said operating chambers against theurging of said resilient expansion coil spring means.
 9. The combinationof a rotary plug valve, an expansible chamber motor actuator and acommon support mounting both said valve and actuator in assembledoperative relationship; said valve including a housing rigidly securedto said support and a control lever to rotate said plug; said actuatorcomprising housing means secured to said support, at least twodiaphragms mounted within said housing to define two operating chambers,one of said chambers located in the space between the two diaphragms,said diaphragms cooperating with said housing to provide fluid tightisolation between said operating chambers, means providing fluidcommunication through said housing into each of said operating chambersfrom the exterior of said housing, motion transmitting means secured atone end to one of said diaphragms exterior of said operating chambersand projecting exterior of said housing, means coacting with saiddiaphragms urging them in a direction causing maximum extension of saidmotion transmitting means from said housing including a collapsibledevice located between and connected to said two diaphragms enablingsaid diaphragms to move relatively away from and toward each otherbetween a substantially fixed maximum distance and a closely spacedadjacent disposition of said two diaphragms; said housing means furthercomprise a spacer ring between said diaphragms urging the peripheries ofsaid diaphragms into fluid seal relationship with said housing, one ofsaid means providing fluid communication into said operating chamberscomprising a portion of said spacer ring and including a fluidpassageway through said spacer ring to said space between the twodiaphragms: additional spacing means located between said diaphragms forpreventing a fluid tight seal of one diaphragm against the other whensaid diaphragms are in said closely spaced adjacent disposition; a pivotconnection between the other end of said motion transmitting means andsaid plug control lever; and said collapsible device permitting tiltingof at least said one of said diapHragms and said motion transmittingmeans relative to said actuator housing means to accommodate an arcuateswinging of said pivot connection about the axis of the rotary plug ofsaid rotary plug valve as the actuator moves said rotary plug through anintermediate flow control position between its operating limitpositions.
 10. The combination of a rotary plug valve, an expansiblechamber motor actuator and a common support mounting both said valve andactuator in assembled operative relationship; said valve including ahousing rigidly secured to said support and a control lever to rotatesaid plug; said actuator comprising housing means secured to saidsupport, at least two diaphragms mounted within said housing to definetwo operating chambers, one of said chambers located in the spacebetween the two diaphragms, said diaphragms cooperating with saidhousing to provide fluid tight isolation between said operatingchambers, means providing fluid communication through said housing intoeach of said operating chambers from the exterior of said housing,motion transmitting means secured at one end to one of said diaphragmsexterior of said operating chambers and projecting exterior of saidhousing, means coacting with said diaphragms urging them in a directioncausing maximum extension of said motion transmitting means from saidhousing including a collapsible device located between and connected tosaid two diaphragms enabling said diaphragms to move relatively awayfrom and toward each other between a substantially fixed maximumdistance and a closely spaced adjacent disposition of said twodiaphragms; a pivot connection between the other end of said motiontransmitting means and said plug control lever; said collapsible devicecomprising diaphragm support plate means secured to each of saiddiaphragms in facing relationship, anchor means on each of said supportplate means, a collapsing link secured to both of said anchor means, andmeans for positively preventing a non-collapsing condition of saidcollapsing link when disposed in its extended position; and saidcollapsing link comprising two U-shaped bails, the stems thereofpivotally connected to said anchor means, said means for positivelypreventing a non-collapsing condition of said link comprising a brackethinging the center portions of said U-shaped bails, and having portionscooperating with said bails limiting extension thereof to less than a180* disposition: said collapsible device permitting tilting of at leastsaid one of said diaphragms and said motion transmitting means relativeto said actuator housing means to accommodate an arcuate swinging ofsaid pivot connection about the axis of the rotary plug of said rotaryplug valve as the actuator moves said rotary plug through anintermediate flow control position between its operating limitpositions.